Shark Bycatch
Elasmobranchs (i.e. sharks, rays, and skates) are one group that can be particularly vulnerable to population-level effects of targeted or incidental catches because of their low biological productivity, which is a product of slow growth, late age at maturity, relatively low reproductive rates, and extended longevity. However, catch estimates for elasmobranchs, have historically been, and remain, poorly documented, making it difficult to quantify total mortality, a crucial component to population status assessments.
Bycatch of seabirds, marine mammals, or sea turtles is not typically sold commercially (although there are exceptions to this). That is not true for sharks: incidentally caught elasmobranchs are commonly retained and may be an important component of landed catch and commercial yield, driven by demand from both national and international markets. That means that the line between elasmobranch target catch and bycatch is often blurry. As catches of many traditionally targeted species decline, fishers are landing more species than ever before, but only a small part of the catch may be officially considered targeted and therefore regulated. This discrepancy results in unmanaged and unmonitored removal of fish, and has prompted calls to redefine bycatch to include both unused catch and any retained catch that is unmanaged (sensu Davies et al. (2009)). What this redefinition highlights is the importance of measuring both discards and retained catch for unmanaged species to assess fisheries impacts on populations and ecosystems. To do that will require data on both elasmobranch discard and retention rates to improve bycatch estimates for particular regions, gear-types and species.
Elasmobranchs (i.e. sharks, rays, and skates) are one group that can be particularly vulnerable to population-level effects of targeted or incidental catches because of their low biological productivity, which is a product of slow growth, late age at maturity, relatively low reproductive rates, and extended longevity. However, catch estimates for elasmobranchs, have historically been, and remain, poorly documented, making it difficult to quantify total mortality, a crucial component to population status assessments.
Bycatch of seabirds, marine mammals, or sea turtles is not typically sold commercially (although there are exceptions to this). That is not true for sharks: incidentally caught elasmobranchs are commonly retained and may be an important component of landed catch and commercial yield, driven by demand from both national and international markets. That means that the line between elasmobranch target catch and bycatch is often blurry. As catches of many traditionally targeted species decline, fishers are landing more species than ever before, but only a small part of the catch may be officially considered targeted and therefore regulated. This discrepancy results in unmanaged and unmonitored removal of fish, and has prompted calls to redefine bycatch to include both unused catch and any retained catch that is unmanaged (sensu Davies et al. (2009)). What this redefinition highlights is the importance of measuring both discards and retained catch for unmanaged species to assess fisheries impacts on populations and ecosystems. To do that will require data on both elasmobranch discard and retention rates to improve bycatch estimates for particular regions, gear-types and species.
